I have just started working with the DNG Profile Editor. In another discussion I commented on the clarity of the instructions provided by the tutorial. I had no difficulty creating a single illuminant profile using the X-Rite color checker passport. But when it came to producing a dual illuminant profile, following the instructions exactly, I was stymied.

At this point one is instructed to "Click the 6500 K-lit ColorChecker image window to select it."

But the 2850K lit image (last loaded) has replaced the 6500K image window (at step 2) and I can find no way to reopen the 6500 K lit image window in order to proceed to the next step.

As a matter of interest, why do these instructions suggest setting the pop-up window in the Chart Pane to "6500K only" and then create color table with first image. Thereafter select second image, set pop-up window to "2850K only" and create color table. I seems to me that, having loaded two images (even if I can only see the second image loaded) one should choose "both color tables" and then create color table. In fact I have tried this and it does produce a profile, but I have no way of determining if it is a correct dual illuminant profile.

After stumbling around I discovered how to move the image windows when two images have been opened. So I can now create a dual illuminant profile following exactly the method described in tutorial #6.

But I also discovered an important prereequisite to making a true dual illuminant profile. After loading the first dng image, pay attention to the Base Profile displayed in the Color Tables pane. I don't know what the default profile is (or even if there is a default), but I can say that one must be sure the selected Base Profile is itself a dual illuminant profile. If the selected Base Profile is a single illuminant profile, then the profile constructed by the PE will also be a single illuminant profile, no matter what procedure one follows in creating the profile. Often (but not always) the "default" Base Profile entry simply states: "Color Checker". Leaving this in place I have gotten inconsistent results.

I also discovered that, after loading 2 dng images, if one selects the Both color tables option in the chart pane and thereafter clicks Create Color Table, the result will not be a dual illuminant profile, unless the Base Profile (as noted above) was a dual illuminant profile.

I base these conclusions on an examination of the dcp files with the software: dcpTool.

Note that the "Both color tables" option always creates a single-illuminant profile. The "Both color tables" option means that the computed color corrections will be applied to both color tables (i.e., the color table for the first calibration illuminant, which is usually Standard Light A, and also the color table for the second calibration illuminant, which is usually D65).

That raises the question: What conditions dictate the choice between a dual illuminant profile and a single illuminant profile created using the "Both color tables" option. (assuming both are created with the same two images at 2850K and 6500K)?

And since I have your attention, may I pose another question:

I have used the PE to create a dual illuminant profile (following tutorial #6). I then make a second dual illuminant profile, using the same pair of images (dng files). When I open an image of the Color Checker in ACR and successively switch between these two profiles, I see some very distinct changes in several of the patches. Is this to be expected, or is it due to some operator error in constructing the profiles?

If you plan to use the profile for a wide range of lighting conditions (generally, I would say "indoor lighting" as well as "natural daylight"), then I suggest building a dual-illuminant profile, where you use the chart shot under indoor lighting for the first color table (2850 K), and you use the chart shot under daylight for the 2nd color table (6500 K).

If you plan to use the profile for a specific lighting condition (e.g., a given studio with a specific set of lights), then I suggest building a single-illuminant profile, using the "Both color tables" option.

Regarding your other question (building two dual-illuminant profiles): How did you build the 2nd dual-illuminant profile? Did you use the same Base Profile (tab 1) as the starting point for the first as well as the second dual-illuminant color profiles?

Thanks for your reply. I am a little puzzled by your suggestion regarding building a profile for a specific lighting condition. Why would one use the "Both Color Tables" option as opposed to choosing a single illuminant option?

Regarding the perceived difference between two "identically" built dual illuminant profiles, I must confess that I had not paid any attention to what was entered as the initial Base Profile, so I am not at all sure that the same value was used in constructing both profiles. I guess I assumed that building a profile based on the Color Checker was, in effect, creating a profile de novo rather than making a modification of an existing profile. If, in fact, the choice of Base Profile makes a difference in the resulting profile (using this protocol), what is the preferred starting Base Profile?

I use a dual-illuminant profile for everyday shooting, especially outdoors or in the decreasingly few incandescent-lit indoor shots, but find the dual-illuminant profile doesn’t work too well for fluorescent lighting or similar glowing-gas-type illumination in institutions and arenas where the tint is significantly different than 0 because neither of the illuminants in the dual-illuminant profile have significantly different than zero tint. As a result, I have a dual-illuminant profile, a few fluorescent/office/arena profiles and some for specific lighting, such as in deep-shade/woods, twilight/after-sunset, moonlight (with sodium vapor streetlights coloring it), or with sodium vapor streetlights. I mostly do nature photography, but for someone shooting people, skintones are important so having a few extra profiles in your pallet can help make things look right.

I specifically name my profiles to include the color-temp/tint values so I can more easily decide which one to use based on the white-balance I have my photos set to.

For example, I made two single-illuminant profiles recently, for a new arena in town, and they are named with a format of: Camera_LightingScenario_ColorK/-Tint.dcp, and specifically: 450D_PinnacleBankArena_2800K-5.dcp and 450D_PinnacleBankArena_4050K38.dcp depending on if just the dimmer, warmer show-centric lights are on or if the brighter, more fluorescent sports lighting is on.

Skin or reds in general would not look good in the brighter arena lighting with a tint of +38 if I had used a standard Tungsten/Cloudy dual-illuminant profile. Besides skintones, sports teams have brightly colored uniforms and they like to see those looking reasonably correct, as well.

DNG Profiles have two color tables, so if you use the both-color-tables option then you are building a single-illuminant profile. The Adobe DNG Profile Editor uses the term Both Color Tables. Perhaps a different program like the one from xrite uses the terms Single-Illuminant and Dual-Illuminant.

The profiles you get from the Adobe product and the xrite product are different, where I believe the Adobe one is newer and creates profiles with hue-twists, whereas the xrite program is older and does not, but I could be wrong, and hopefully Eric can clarify at least what the DNG Profile Editor does regarding hue-twists.

Following on Eric's remark, that, in constructing any profile, one should pay attention to the Base Profile entry in the Color Table Pane. I decided to investigate the default behavior of this entry.

Immediately after opening PE this entry shows "none"

After opening the first dng image the entry shows the first (camera compatible) profile in the alphabetically ordered Base Profile drop down list. (often, but not always, Adobe Standard, depending on the name of other profiles you may have exported.)

When a second dng image is opened the Base Profile entry does not change, regardless of the source (camera) of the second image.

When all images are removed (File > Close All DNG Images) the Base Profile entry is persistent (sticky), and does not change upon opening a new dng image, regardless of the source of that image.

In working with the PE I have discovered some significant and interesting effects of the Base Profile selection on the structure of the resulting edited profile. I have a hunch that this is not the proper forum for a discussion of these observation; so I thank the moderators for the tolerance extended thus far.

I have been trying to create a DNG profile from scratch but it seems it's no possible because you always need to use the base profile.

I usually go into PE, load a DNG image, select the base profile, add just one random color patch and save it as a new camera profile. Then I convert the color profile dcp to xml to be edited and I delete all color tables and tone curve. Then I recompile the xml file to dcp again and load it under PE. Then you can start adding the new tone curve and creating both color tables for 2850 and 6500. This is fine and works! I also would like to use my own color matrices but ... this is where the whole problem starts. Why do I want to use my own color matrices? Well because I don't want to create a color profile that matches real colors. I want to create my own Reversal Film color and if I can't start with an accurate ColorMatrix that corrects the whole color spectrum as I want, it's more difficult to correct it later with color tables. So I need my ColorMatrix and ForwardMatrix. Would you mind please telling us how to calcualte ForwardMatrix from the ColorMatrix? Because if I use this formula...

CameratoXYZ_D50 = CA * CameraToXYZ

I doesn't work. I understand CameraToXYZ_D50 is the ForwardMatrix and ColorMatrix is "CameraToXYZ"

Note that the "Both color tables" option always creates a single-illuminant profile. The "Both color tables" option means that the computed color corrections will be applied to both color tables (i.e., the color table for the first calibration illuminant, which is usually Standard Light A, and also the color table for the second calibration illuminant, which is usually D65).

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After playing around with the Profile Editor for a while, and examining the results with dcpTool, I now understand (I hope) what Eric is saying. In his language a single-illuminant profile is one created from a single dng image using the "both color tables" option (without regard to the illuminant used to capture that image.) When one does this (using Adobe Standard as the base profile) an examination of the resulting profile with dcpTool shows the following:

Two illluminants are identified: 17 (Std A) and 21 (D65).

Color Matrix 1 & 2; Forward Matrix 1 & 2; Hue Sat Delta Tables 1 & 2.

Which certainly gives the impression of a dual illuminant profile to novices like myself. My guess is that the PE software itself applies a default assumption of these two illuminants, corrects the image for each illuminant and constructs two color tables, one for each illluminant. When used, the profile will interpolate between the two tables based on the white balance of the image being edited.

If this is indeed correct it makes me wonder in what way does such a profile differ from a dual illuminant profile created from two dng images, each captured under a different illuminant (2800K & 6500K) as described in Tutorial #6 of the PE instructions. These instructions contain the following description of such a dual illuminant profile: "The result is a single profile that performs well under a wide range of illuminants instead of a single fixed illuminant." Which really make me scratch my head. Should one conclude from this that a single illuminant profile (created using the "both color tables" option) will perform less well under a range of illuminants? Will it perform well only under a narrow range of illuminants centered around the illuminant used to capture the single image?

As a footnote, it is worth remarking that I (and perhaps others) have been confused by examining profiles created by the XRite software when using only a single dng image. Examining such a profile with dcpTool one sees the following structure:

One illuminant only #23 (D50)

A single Color Matrix table.

A single Hue Sat Delta Table.

Thus one comes to expect this structure in a single illuminant profile.

Thanks for your comments. What you write does indeed make sense. Nevertheless I remain a bit confused by the structure (as reported by dcpTool) of a single illuminant profile created with the "both color tables" option (see what I have reported above). The profile is undoubtedly constructed using a single dng image, thus a single illuminant must have been used in capturing the image. Nevertheless the profile contains two color tables which, by the way, are clearly not identical? Why does dcpTool report two illuminants? Is it possible that LR/ACR does some interpolation between the two tables before applying the profile, perhaps based on something other than WB value?

What is different between the two tables of a single-illuminant profile from the DNGPE? It has been my assumption that the two tables have the same values other than the illuminant so any interpolation will result in the same values for whatever WB is used.

Glad you asked. I have compared the values in the two tables. The Hue Shift values differ significantly at many but not all positions. The values of the SatScale and ValScale differ but the differences are generally small, in the range of 0.01 - 0.09. So it is quite apparent that the two tables are not identical. What process leads to the creation of two different tables is an interesting question.

However, when all is said and done, the bottom line for me is the fact that a PE created single illuminant table (@ about 5200K) yields much more pleasing tones in my images when compared to any of the Adobe canned profiles.

In my opinion the reason why Illuminant-A and D65 tables are very similar is because color matrices are the ones that correct color cast. Let me explain myself better:

Imagine a 5000K image. RGB channels are at the same level when white balance. If you go down towards 2850 K, red channel predominates and in order to white balance, you gotta increase the blue channel. That's why noise increases in the blue channel. On the other hand when you go towards D65, blue channel predominates. Color Matrix corrects that! but once everything is neutralized, there are minor differences between color tables for 6500 and 2850. This is my theory of how Lightroom is working.

I have been working for a while with DNG PE, trying to create a really good color profile and I have found that color matrices for Standard Illuminant-A are incorrect, that's why single illuminant color profiles work better for a specific color temperature because there is no interpolation between the correct matrix for D65 and the incorrect one for Standard Illuminant-A.

DNG profiles are a great idea for color correcting but taking into account the huge amount of cameras Adobe has to profile, they cannot spend too much time with every camera in order to create a really good color profile.